The present invention relates to a rotation controller and a rotation control method. More particularly, the invention relates to a rotation controller and a rotation control method for adjusting the speed of a rotary member upon rotating any of various rotary members by the use of a spiral spring, an engine, electric power or human power.
Japanese Examined Patent Publication No. 07-119812 discloses one of the known electronically controlled mechanical watches based on a process comprising converting mechanical energy produced upon release of a spiral spring into electric energy by means of a generator, causing rotation control means to operate with this electric energy, and controlling the value of current flowing through a coil of the generator, thereby accurately driving a needle fixed to a train wheel and thus accurately displaying the time.
In the disclosed electronically controlled mechanical watch, the rotational speed of the generator is controlled by entering a signal based on the rotation of a rotor of the generator into a counter, entering on the other hand a signal from a crystal oscillator as well into the counter, comparing values from the individual counters, and controlling the generator on the basis of the resulting difference between these values. The counter is one known as an integral counter which compares the phase difference between reference clock pulse (Ref-pulse) and generator rotation period pulse (G-pulse), down-counting the U/D counter when G-pulse is gain, and up-counting the same if G-pulse is in loss.
At the time when a value obtained by measuring the time of one period of Ref-pulse agrees with a value obtained by the integral counter, the generator is braked, and braking is continued until the completion of time measurement of one period of Ref-pulse. The value of the integral counter would therefore sets the brake releasing time. More specifically, the value of the integral counter comprises an integrated value of the brake releasing time at which the average speed of G-pulse agrees with the target speed (Ref-pulse). That is, this system adopts integral control.
However, because the integral control method as described above is based on comparison of signals output during a period while counting them with the counter, it is possible to adjust the average speed of the rotor to a set time for a sufficiently long period of time, thus ensuring substantially constant speed control of operations. The rotation speed of the rotor cannot however be adjusted immediately, leading to a low response. In addition, this method has another problem in that a slight phase difference is produced before alignment with a target frequency be cause of the relationship between the force of the spiral spring and the braking force.
More specifically, integral control can be expressed by a block diagram shown in FIG. 26. In general, the transfer function used in a generator or a motor is known to be 1/s (sT+1). As shown in FIG. 26, this is composed of a primary delay transfer function 601 of 1/(sT+1) and an integral term 602 of 1/s. An integrating factor is therefore included in the generator itself to be controlled. Bode diagrams for a case where only integral control is applied to an object of control are shown in FIGS. 27 and 28.
In these Bode diagrams, conditions required for stabilizing rotation control are that the phase upon a phase margin, i.e., 0 db (gain crossing point) is ahead of xe2x88x92180xc2x0, and that the gain upon gain margin, i.e., with a phase of xe2x88x92180xc2x0 (phase crossing point) is up to 0 db.
For integral control alone, however, there occurs a delay of xe2x88x9290xc2x0 for the object to be controlled, and an additional delay of xe2x88x9290xc2x0 as a result of integral control, as shown in FIG. 27. The phase characteristic is therefore that near xe2x88x92180xc2x0. It is consequently difficult to ensure stable control because a phase margin or a gain margin is unavailable from the integral control alone. In the watch disclosed in Japanese Examined Patent Publication No. 07-119812, therefore, it is necessary perform control with a very low frequency, and the resultant response is 0.016 Hz or under.
A case where the gain of the integral counter is assumed to be increased to 100 times as large is illustrated in FIG. 28. In this case also, the phase margin is later than xe2x88x92180xc2x0, so that a stable control cannot be expected.
As is clear from the information described above, the conventional control through integral control alone permits average speed adjustment, but involves a problem in that the phase deviation cannot be solved.
Another problem is that it is almost impossible to cope with a sudden disturbance encountered upon production of acceleration in a wristwatch by shaking the arm, because of the slow response of control.
Further, in the above-mentioned watch, using a spiral spring as power, the rotational force largely varies with the extent of winding. This causes a control error which in turn results in a loss or a gain of the watch. When using the watch as a wristwatch, movement of the arm causes an acceleration of the rotor, leading to a disturbance which causes an instable control status, resulting in a change in movement of the needle or a gain or a loss.
Since such an integral control is popularly utilized for controlling a rotary member, these problems are similarly encountered when controlling various rotary member requiring speed adjustment control, not limited to a watch, but including, for example, various toys comprising a rotary member such as a doll rotating under the action of a spiral spring, the drum of a music box, and an electric motor of a hybrid car based on a combination of a gasoline engine and an electric motor.
A first object of the present invention is to provide a rotation controller and a rotation control method which can solve a phase deviation of a rotary member, give a fast response of a control system, and are highly resistance to disturbance.
A second object of the invention is to provide a rotation controller and a rotation control method which permit downsizing of circuit scale and simplification of circuit configuration so as to be applicable to a small device such as a wristwatch.
Disclosure of Invention
The rotation controller of the present invention controlling the rotation period of a rotary member by applying a brake on the rotating rotary member by power supplied from a power source, comprising: rotation detecting means generating a rotation signal corresponding to revolutions of a rotary member; target signal generating means generating a target signal corresponding to target revolutions of the rotary member; phase difference compensating means detecting a phase difference between a rotation signal output by the rotation detecting means and a target signal output by the target signal generating means, and generating a phase difference compensating signal serving as a brake control signal; frequency difference compensating means detecting a frequency difference between the rotation signal and the target signal, and generating a frequency difference compensating signal serving as a brake control signal; and brake control means controlling the manner of braking by means of at least any one of the phase difference compensating signal from the phase difference compensating means and the frequency difference compensating signal from the frequency difference compensating means.
In the present invention, phases are compared between the rotation signal of the rotary member and the target signal of that rotary member, and a phase difference compensating signal serving as a brake control signal is entered into the braking circuit of the rotary member on the basis of the resultant phase difference, thus permitting achievement of a manner of control known as the phase synchronizing circuit control, i.e., PLL (phase-locked loop) control. It is therefore possible to set a braking level by comparing rotation signal waveforms between individual periods of the rotary member. A stable control system having a high response can be achieved if it is once adjusted within a locking range unless there if instantaneously a large change in signal waveform, and it is furthermore possible to eliminate a phase deviation.
Further, the frequency difference compensating means is provided in addition to the phase difference compensating means. Therefore, when the control comes off the locking range of PLL control as immediately after start of rotation control of the rotary member, control can be performed so as to bring the speed difference closer to 0 while disregarding the phase difference between a rotation signal and a target signal by the use of the frequency difference compensating means, thus making it possible to quickly adjust rotation of the rotary member within the locking range. By applying rotation control by the use of the phase difference compensating means after bring the speed difference closer to 0 with this frequency difference compensating means, therefore, it is possible to a larger phase deviation as compared with the control by the phase difference compensating means alone from being accumulated, and quickly accomplish speed adjustment control of the rotary member.
In the aforementioned rotation controller, it is desirable that the frequency difference compensating means has frequency difference compensation retaining means; that the brake control means has two control modes for a control starting stage immediately after start of rotation control and a constant stage when rotation control is stable; that, in the control starting stage, rotation control is performed in response to a frequency difference compensating signal from the frequency difference compensating means; and that, in the constant control stage, brake control is conducted in response to a sum signal of a frequency difference compensating signal retained by the frequency difference compensation retaining means upon switching the control starting stage to the constant control stage after stabilization of rotation control and the phase difference compensating signal.
In the invention, rotation control in the control starting stage is carried out on the basis of the frequency difference compensating signal from the frequency difference compensating means. Even when the revolutions of the rotary member largely deviate from the target revolutions, therefore, it is possible to quickly approach the target revolutions and conduct rotation control with a high response.
Further, in the constant control stage, rotation control is conducted by the use of a sum signal of the frequency difference compensating signal and the phase difference compensating signal. It is therefore possible to set an approximate amount of braking from the frequency difference compensating signal. Because it suffices, with the phase difference compensating signal, to set an amount of braking for fine control which cannot be effected with the frequency difference compensating signal, it is possible to quickly determine the optimum amount of control by summing up the individual signals, thus permitting further improvement of response in the rotation control.
In addition, since the frequency difference compensating signal is required only to permit calculation of an approximate amount of braking, the configuration of the frequency difference compensating means can be simplified.
In the control starting stage, the brake control means may determine from a difference in frequency that rotation control has been stabilized. Determination from the frequency difference makes it possible to accurately and relatively easily determine that rotation control has been stabilized, thus permitting appropriate switching of control independently of dispersions of the rotary member.
In the control starting stage, the brake control means may deem the rotation control to have been stabilized upon the lapse of a certain predetermined period of time from the start of control, and may switch over control from the control starting stage to the constant control stage. By making a determination with time, the circuit configuration can be made simpler than in determination from the frequency difference, and the circuit can easily be downsized, thus permitting easy application for compact devices such as a wristwatch, or other timepiece.
It is desirable that the phase difference compensating means comprises phase difference detecting means and compensating signal generating means for receiving an output therefrom; that the rotation signal and the target signal have a repeated pulse waveform; and that the phase difference detecting means has a counter which performs an addition or a subtraction at rise or fall of the target signal, and a subtraction or an addition at rise or fall of the rotation signal so as to sum up the member of rises or falls of each signal, and outputs an output of the counter as a phase difference signal.
When the phase difference detecting means comprises a counter, it is possible to easily achieve a simple circuit configuration, and hence a more compact device, and thus to reduce the cost. Further, because it is possible to use a counter capable of retaining a plurality of counter values, phase differences can be detected in a wide range. Possibility to retain cumulative values thereof even when phase differences are cumulated makes it possible to perform a control meeting a cumulative phase difference, leading to a more accurate speed adjusting control.
It is further desirable that the phase difference compensating means further comprises a phase difference compensating filter having an integrating function; and that the phase difference compensating filter comprises a sign detecting circuit detecting a sign of the phase difference signal, a frequency divider dividing frequency with a dividing ratio variable depending upon the absolute value of the phase difference signal, and a counter adds or subtracts an output of the frequency divider with the sign. In this case, the phase difference compensating filter serves as a compensating signal generating means, and a counter output serves as a phase difference compensating signal.
Since the dividing ratio of the frequency divider with the absolute value of the phase difference signal is made variable, it is possible to set an appropriate magnitude of the phase difference compensating signal, depending upon the extent of the phase difference, thus permitting control so as to quickly eliminate the phase difference.
The rotary member may be the generator in an electrically controlled mechanical timepiece comprising a mechanical energy source, a generator, driven by the mechanical energy source connected via a train wheel, generating an induced power and thus supplying electric energy, and a pointer connected to the train wheel. When applying the invention to such an electronically controlled mechanical timepiece, and upon resuming needle operation after needle alignment from stoppage of the generator for needle alignment, it is possible to quickly cause the generator rotation to meet target revolutions (for example, reference frequency from a crystal oscillator), and quickly switch to an accurate needle operation.
Further, the rotary member may be a rotary member in a toy comprising a mechanical energy source an operating member such as a doll driven by the mechanical energy source connected via a power transmitting mechanism, and a rotary member rotated in linkage with this operating member.
The rotary member may also be the motor in a toy comprising an electric energy source, and a motor driven by the electric energy source.
By applying the present invention to various toys as described above, it is possible to accurately and quickly control the rotation speed of a rotary member or a motor, cause a change in the rotation speed in response to operation by a child playing with the toy, and perform high-level play even upon occurrence of a change.
The rotary member may be the generator in a hybrid car comprising an engine, and a generator serving also as a motor driven by the engine. By applying the invention to such a hybrid car, it is possible, upon conducting auto-cruising control, for example, to perform speed adjustment without largely changing the engine output, by rotating the generator at the target revolutions, and to reduce the fuel consumption.
The rotation control method of the present invention for controlling the rotation period of a rotary member by braking the rotary member rotated by a power supplied by a power source, comprising the steps of: detecting a phase difference by comparing a rotation signal corresponding to revolutions of the rotary member and a target signal corresponding to target revolutions of the rotary member; detecting a frequency difference between the rotation signal and the target signal; and controlling a brake of the rotary member by means of at least one of a phase difference compensating signal corresponding to the phase difference and a frequency difference compensating signal corresponding to the frequency difference.
In the present invention, the rotary member is controlled by a combination of phase synchronization circuit control (PLL control) and frequency difference control. This permits quick speed adjustment control of the rotary member, and achievement of a stable control of the rotary member with a high response.
This method should preferably comprises the steps of: conducting brake control of the rotary member by means of the frequency difference compensating signal in a control starting stage immediately after start of rotation control; upon stabilization of rotation control, switching over the control to the constant control stage while retaining the frequency difference compensating signal at this point; and in the constant control stage, performing brake control of the rotary member by means of an addition signal of the retained frequency difference compensating signal and the phase difference compensating signal.
In the method of the invention, rotation control is carried out by means of the frequency difference compensating signal in the control starting stage, and rotation control is conducted by the use of the sum signal of the frequency difference compensating signal and the phase difference compensating signal in the constant control stage. Even when the revolutions of the rotary member largely deviate from the target revolutions upon starting control, therefore, it is possible to quickly bring the revolutions closer to the target revolutions, thus permitting high-response rotation control. In the constant control stage, the amount of braking can be finely adjusted with the phase difference compensating signal after setting an approximate amount of braking with the frequency difference compensating signal. It is therefore possible to quickly determine an optimum amount of control and thus further improve response of rotation control.
In the rotation control method of the invention, stabilization of the rotation control in the control starting stage may be determined from a frequency difference. In the control starting stage, rotation control may be deemed to have been stabilized upon the lapse of a certain predetermined period of time from the start of control, and control may be switched over from the control starting stage to the constant control stage.